1. Field of the Invention
This invention relates to new 3-hydroxyflavones variously substituted on the oxygen in the 3 position, the method of preparing them and their therapeutic application.
The new products, which are the object of this invention, have the general formula ##STR1## where R.sub.1 is H or OH and R.sub.2 is a lower alkoxy of C.sub.2 to C.sub.6, a cycloalkoxy of C.sub.5 to C.sub.8, a methanesulfonyloxy or a paratoluenesulfonyloxy, provided that R.sub.1 is not OH if R.sub.2 is a lower alkoxy of C.sub.2 to C.sub.4.
The products where R.sub.1 is OH are quercetin derivatives; the products where R.sub.1 is H are fisetin derivatives.
Some methyl ethers of flavonols and in particular 3-O-methyl flavanols are already known. A certain number of these are natural derivatives. The Biosedra company on May 21, 1970 under No. 70 18458 patented pentabenzylquercetin used in therapy in the standard indications of flavonoids (inhibition of hyperpermeability and reduction of capillary fragility).
The Hoffman-la-Roche company filed on 4/9/1980, under British priority of 4/10/1979, a European Pat. No. 19081 describing 3-alkoxy-5,7-dihydroxyflavones having antiviral activity and in particular products answering general formula I with R.sub.1 being OH and R.sub.2 being a lower alkoxy of C.sub.1 to C.sub.4 and preferably equal to methoxy or ethoxy. These products are, however, distinct from the compounds of the present invention.